Field of the Invention
The present invention relates to an electromagnetic fuel injection valve comprising a valve housing that has a valve seat in one end part thereof, a hollow fixed core that is provided so as to be connected to the other end of the valve housing, a coil that is disposed on an outer periphery of the fixed core, a valve body that is formed by having a stem provided so as to be connected to a valve part that operates in cooperation with the valve seat, a movable core that is slidably fitted onto the stem while being disposed so as to oppose an attracting face of the fixed core, a valve-open side stopper that is fixed to the stem so that, by making the movable core, that is attracted to the attracting face when the coil is energized, abut against the valve-open side stopper, the valve body is made to undergo a valve-opening operation, a valve-closed side stopper that is fixed to the stem further on the valve seat side than the valve-open side stopper so as to restrict a stroke of the movable core along the stem between the valve-closed side stopper and the valve-open side stopper, a valve spring that urges the valve body in a valve-closing direction, and an auxiliary spring that is provided between the valve-open side stopper and the movable core so as to exhibit a spring force that makes the movable core move away from the valve-open side stopper and abut against the valve-closed side stopper when the coil is not energized.
Description of the Related Art
Such an electromagnetic fuel injection valve is known in Japanese Patent Application Laid-open No. 2013-104340.
In such an electromagnetic fuel injection valve, when the valve opens, it is only the movable core that slides on the stem of the valve body and is attracted toward the fixed core side; after being accelerated, the movable core pushes upward the valve-open side stopper fixed to the stem against a set load of the valve spring, thus enabling the valve body to be opened promptly, and valve-opening responsiveness of the valve body can be enhanced. Furthermore, when the valve closes, the movable core urged by means of the auxiliary spring abuts against the valve-closed side stopper, and an amount of rearward rebound of the valve body due to a seating impact when the valve body is seated on the valve seat for the first time can be minimized.
An interior of the electromagnetic fuel injection valve is filled with fuel; in a valve-closed state in which the movable core abuts against the valve-closed side stopper, fuel is present in a very small gap between the movable core and the valve-closed side stopper, and viscosity of the fuel acts as a resistance during a valve opening operation of the valve body. However, in the arrangement disclosed in Japanese Patent Application Laid-open No. 2013-104340 described above, the valve-closed side stopper member is formed into a cylindrical shape having the same external diameter along its whole length, a region in which the movable core and the valve-closed side stopper abut against each other is relatively wide, the valve-opening resistance due to the viscosity of the fuel is relatively large, and there is a possibility that the valve-opening responsiveness will be degraded.
On the other hand, even in a valve-open state in which the movable core abuts against the valve-open side stopper, fuel is present in a very small gap between the movable core and the valve-open side stopper, and the viscosity of the fuel acts as a resistance during a valve closing operation of the valve body, but responsiveness during a valve closing operation is more affected by residual magnetism generated when stopping energization of the coil than by the viscosity of the fuel.